Checkpoint inhibitor pneumonitis (CIP) is an immunerelated adverse event that can occur after initiation of anti-programmed death 1/programmed death ligand 1 immune checkpoint inhibitor (ICI) therapy for the treatment of multiple malignancies, including NSCLC. However, the incidence of CIP has not been previously examined in a population that included both trial-enrolled and non-trialenrolled patients with advanced NSCLC. Furthermore, risk factors and other clinical characteristics associated with CIP severity are not known. In this study, we retrospectively examined clinical characteristics, incidence, and risk factors for CIP in a cohort of 205 patients with NSCLC, all of whom received anti-programmed death 1/programmed death ligand 1 ICIs. Our results demonstrate a higher incidence of CIP (19%) than previously reported in clinical trials (3%-5%). Our data also suggest that tumor histologic type may be a risk factor for CIP development. We observed a wide range of time to onset of CIP (median 82 days), with high morbidity and mortality associated with higher-grade CIP regardless of degree of immunosuppression. Our data provide new insight into the epidemiology and clinical

IMPORTANCEThe spectrum of individual immune-related adverse events (irAEs) from anti-programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) immune checkpoint inhibitors (ICIs) has been reported widely, and their development is associated with improved patient survival across tumor types. The spectrum and impact on survival for patients with non-small cell lung cancer (NSCLC) who develop multisystem irAEs from ICIs, has not been described. OBJECTIVE To characterize multisystem irAEs, their association with survival, and risk factors for multisystem irAE development. DESIGN, SETTING, AND PARTICIPANTSThis retrospective cohort study carried out in 5 academic institutions worldwide included 623 patients with stage III/IV NSCLC, treated with anti-PD-(L)1 ICIs alone or in combination with another anticancer agent between January 2007 and January 2019. EXPOSURES Anti-PD-(L)1 monotherapy or combinations.MAIN OUTCOMES AND MEASURES Multisystem irAEs were characterized by combinations of individual irAEs or organ system involved, separated by ICI-monotherapy or combinations. Median progression-free (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Differences in PFS and OS between irAE groups were assessed by multivariable models. Risk for multisystem irAE was estimated as odds ratios by multivariable logistic regression. RESULTSThe 623 patients included in the study were mostly men (60%, n = 375) and White (77%, n = 480). The median (range) age was 66 (58-73) years, and 148 patients (24%) developed a single irAE, whereas 58 (9.3%) developed multisystem irAEs. The most common multisystem irAE patterns in patients receiving anti-PD-(L)1 monotherapy were pneumonitis thyroiditis (n = 7, 14%), hepatitis thyroiditis (n = 5, 10%), dermatitis pneumonitis (n = 5, 10%), and dermatitis thyroiditis (n = 4, 8%). Favorable Eastern Cooperative Oncology Group (ECOG) performance status (PS) (ECOG PS = 0/1 vs 2; adjusted odds ratio [aOR], 0.27; 95% CI, 0.08-0.94; P = .04) and longer ICI duration (aOR, 1.02; 95% CI, 1.01-1.03; P < .001) were independent risk factors for development of multisystem irAEs. Patients with 1 irAE and multisystem irAEs demonstrated incrementally improved OS (adjusted hazard ratios [aHRs], 0.86; 95% CI, 0.66-1.12; P = .26; and aHR, 0.57; 95% CI, 0.38-0.85; P = . 005, respectively) and PFS (aHR, 0.68; 95% CI, 0.55-0.85; P = .001; and aHR, 0.39; 95% CI, 0.28-0.55; P < .001, respectively) vs patients with no irAEs, in multivariable models adjusting for ICI duration. CONCLUSIONS AND RELEVANCEIn this multicenter cohort study, development of multisystem irAEs was associated with improved survival in patients with advanced NSCLC treated with ICIs.